You are what you throw away

WASTE can be a revelation. Excavations of old rubbish tips (or middens, as archaeologists call them) provide much of our knowledge of everyday life in the past. Many ancient civilisations piled up mountains of garbage. At a spot in America called Pope's Creek, on the shores of the Potomac river, oyster shells discarded by the pre-Columbian inhabitants cover an area of 30 acres (12 hectares) to an average depth of ten feet. Enormous shell middens can be found all over the world, wherever ancient migrants came across handy oyster and mussel beds.

Archaeologists have found papyruses inscribed with parts of lost plays by Sophocles and Euripides in a Greco-Roman rubbish tip in Egypt. The same site, near the ancient town of Oxyrhynchus, yielded a wealth of 2,000-year-old invoices, receipts, tax returns and other documents.

Modern waste can be equally enlightening. Dustbins generally provide a more honest account of their owners' behaviour than do the owners themselves. A research programme at the University of Arizona conducted several studies comparing the participants' own assessments of their habits with the record provided by their rubbish. It turned out that people wasted much more food than they realised, claimed to cook from scratch more often than they really did and ate more junk food and less virtuous stuff than they admitted. For example, they overestimated their consumption of liver by 200%. A survey on consumption of red meat was particularly telling. Rich households, perhaps wanting to be seen to be eating healthily, claimed to consume less of it than they did, whereas poor ones, possibly indulging in wishful thinking, claimed to eat more.

The project uncovered many other oddities of human behaviour. For example, a well-publicised shortage of a particular product actually causes people to throw more of it away, perhaps because they have bought too much of it. Similarly, a public campaign to get people to take hazardous waste to special collection points makes them put more of it in the bin. Such campaigns seem to prompt them to have a clear-out but they often do not make it to the collection point.

Don't ask, dig

Waste can be used to determine with great accuracy how many people are living in a particular place, how old they are, how much they earn and which ethnic group they come from. America's Census Bureau has toyed with the idea of using data derived from analyses of household rubbish to adjust its survey data. America's Supreme Court has also acknowledged the importance of waste, ruling that police may rummage through trash left out for collection without a warrant.

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